Surgical instrument guide

ABSTRACT

An instrument guide is removably inserted into a proximal portion of a cannula and extends to a distal end of the cannula to guide and support multiple surgical instruments within the cannula. The instrument guide is designed to be manufactured by injection molding of plastic material. The instrument guide includes a tube and several radial walls connected to the tube to form passageways within the tube. The radial walls are joined to a core where they intersect. The tube and radial walls have substantially the same wall thickness and the core has a minimum diameter that is substantially larger than the wall thickness to facilitate delivery of plastic material. Portions of the tube and radial walls are thinner than the general wall and rib thickness to form guideways that support surgical instruments within the passageways. Channels may be formed on an outside of the tube to deliver insufflation gas.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Filing under 35 U.S.C. 371from International Application No. PCT/US2017/041782, filed on 12 Jul.2017, and published as WO 2018/013730 A2 on 18 Jan. 2018, which claimsthe benefit pursuant to 35 U.S.C. 119(e) of U.S. Provisional ApplicationNo. 62/361,934, filed 13 Jul. 2016, each of which application isspecifically incorporated herein, in its entirety, by reference.

BACKGROUND Field

Embodiments of the invention relate to the field of endoscopic surgicalinstruments and, in particular, to instrument guides for endoscopicsurgical instruments that are suited for manufacturing methods such asby injection molding of plastic.

Background

Minimally invasive medical techniques have been used to reduce theamount of extraneous tissue which may be damaged during diagnostic orsurgical procedures, thereby reducing patient recovery time, discomfort,and deleterious side effects. Traditional forms of minimally invasivesurgery include endoscopy. One of the more common forms of endoscopy islaparoscopy, which is minimally invasive inspection or surgery withinthe abdominal cavity. In traditional laparoscopic surgery, a patient'sabdominal cavity is insufflated with gas, and cannula sleeves are passedthrough small (approximately 12 mm) incisions in the musculature of thepatient's abdomen to provide entry ports through which laparoscopicsurgical instruments can be passed in a sealed fashion.

The laparoscopic surgical instruments generally include a laparoscopefor viewing the surgical field and surgical instruments having endeffectors. Typical surgical tools include clamps, graspers, scissors,staplers, and needle holders, for example. The surgical instruments aresimilar to those used in conventional (open) surgery, except that theend effector of each surgical instrument is separated from its handle byan approximately 30 cm. long extension tube, for example, so as topermit the operator to introduce the end effector to the surgical siteand to control movement of the end effector relative to the surgicalsite from outside a patient's body.

To reduce the trauma of minimally invasive surgery even further,techniques are being developed to allow minimally invasive surgery usingonly a single access port into the body, such as a single incision orsingle natural body orifice. This access may be accomplished by using asomewhat larger cannula that can accommodate all of the instrumentsrequired for the surgery. Minimally invasive surgery performed through asingle incision or natural orifice may be referred to as single portaccess (SPA) surgery. The single cannula that provides the single portmay be introduced through a body orifice or through an incision.

If multiple surgical instruments and/or camera instruments areintroduced to a surgical site through a single cannula, an instrumentguide may be inserted into the cannula to support and guide theinstruments within the cannula. It is desirable to use as small acannula as possible, consistent with the size of the instruments to bepassed through the cannula. Therefore, it is desirable to make the wallsof the instrument guide thin.

Equipment that is introduced to a surgical site must be sterile.Sterilization of surgical equipment for reuse is expensive and it isdifficult to ensure a consistent effectiveness of the procedures. Usinginexpensive single use equipment eliminates the need for sterilizationin the field.

Plastic parts can be produced inexpensively by injection molding.However, a part must be designed to meet a variety of constraints to besuitable for production by injection molding because it is necessary tobe able to fill a mold with heated plastic material that flows into themold. One constraint is that all areas of the part should be ofsubstantially the same thickness to avoid deformations such asshrinkage, warp, surface irregularities, or other inaccuracies thatmight make the part non-functional. Another constraint is that thinwalls have to be limited in length because of the tendency of theplastic material to harden quickly within a thin wall. And, anynecessary transitions from one thickness to another should be carefullydesigned to minimize internal stress in the cooled part. But because offunctional requirements, the required length of an instrument guide isdifficult to achieve without making the walls of the guide thick, and sowould require a cannula with a relatively larger inner diameter andcorrespondingly a relatively larger incision.

It would be desirable to have an instrument guide that is designed tohave both sufficient length and thin walls while being capable ofproduction by a manufacturing method such as injection molding ofplastic material.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention by way of example and not limitation. Inthe drawings, in which like reference numerals indicate similarelements:

FIG. 1 is a view of an illustrative teleoperated surgical system.

FIG. 2 is a pictorial view of an unassembled access port.

FIG. 3 is a side view of assembled access port with a portion of thecannula cut away to show the instrument guide that is inserted into thecannula.

FIG. 4 is a cross-section of the instrument guide taken along line 4-4in FIG. 3 .

FIG. 5A is a cross-section of the instrument guide taken along line 5-5in FIG. 3 .

FIG. 5B is an enlarged cross-section of the instrument guide taken alongline 5-5 in FIG. 3 .

FIG. 6 is a schematic side view of the instrument guide inserted intothe cannula to illustrate the flow of insufflation gas.

FIG. 7 shows a cross-section of the outside surfaces of a camerainstrument and three additional surgical instruments and the outsidesurface of the instrument guide.

FIG. 8 shows a cross-section of an instrument guide in which wallthicknesses have been increased.

FIG. 9 shows a cross-section of the instrument guide radial walls havebeen joined by a radius.

FIG. 10 shows a cross-section of the instrument guide in which channelsfor insufflation gas have been added to the outside surface of theinstrument guide.

FIG. 11 shows a side view of an exemplary instrument guide.

FIG. 12 shows an end view of the exemplary instrument guide of FIG. 11 .

FIG. 13 shows a cross-section view of the exemplary instrument guidetaken along line 13-13 in FIG. 12 .

FIG. 14 shows a schematic representation of a mold that can be used toproduce an instrument guide by injection molding.

DESCRIPTION OF EMBODIMENTS

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the invention may bepracticed without these specific details. In other instances, well-knowncircuits, structures, and techniques have not been shown in detail inorder not to obscure the understanding of this description.

In the following description, reference is made to the accompanyingdrawings, which illustrate several embodiments of the present invention.It is understood that other embodiments may be utilized, and mechanicalcompositional, structural, electrical, and operational changes may bemade without departing from the spirit and scope of the presentdisclosure. The following detailed description is not to be taken in alimiting sense, and the scope of the embodiments of the presentinvention is defined only by the claims of the issued patent.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention.Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper”, and the like may be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the figures. It will be understood thatthe spatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(e.g., rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein interpreted accordingly.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising” specify the presence of stated features, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, steps, operations,elements, components, and/or groups thereof.

The term “object” generally refers to a component or group ofcomponents. For example, an object may refer to either a pocket or aboss of a disk within the specification or claims. Throughout thespecification and claims, the terms “object,” “component,” “portion,”“part” and “piece” are used interchangeably.

The terms “or” and “and/or” as used herein are to be interpreted asinclusive or meaning any one or any combination. Therefore, “A, B, or C”or “A, B, and/or C” mean “any of the following: A; B; C; A and B; A andC; B and C; A, B, and C.” An exception to this definition will occuronly when a combination of elements, functions, steps, or acts are insome way inherently mutually exclusive.

Terms of approximation, such as “substantially” and “about,” as usedherein are to be interpreted as meaning equal to a stated amount withina tolerance that is appropriate to the manufacturing processes thatproduces the stated amount or to the use or requirement for the statedamount. Thus a length that is substantially a stated amount could be thestated amount plus or minus a small amount if the length is produced bya precise process or represents a critical dimension. Conversely, alength that is substantially a stated amount could be the stated amountplus or minus a large amount if the length is produced by an impreciseprocess or represents a non-critical dimension.

The terms “instrument” and “surgical instrument” are used herein todescribe a medical device configured to be inserted into a patient'sbody and used to carry out surgical or diagnostic procedures. Thesurgical instrument typically includes an end effector associated withone or more surgical tasks, such as a forceps, a needle driver, ashears, a bipolar cauterizer, a tissue stabilizer or retractor, a clipapplier, an anastomosis device, an imaging device (e.g., an endoscope orultrasound probe), and the like. Some instruments used with embodimentsof the invention further provide an articulated support (sometimesreferred to as a “wrist”) for the surgical tool so that the position andorientation of the surgical tool can be manipulated with one or moremechanical degrees of freedom in relation to the instrument's shaft.Further, many surgical end effectors include a functional mechanicaldegree of freedom, such as jaws that open or close, or a knife thattranslates along a path. Surgical instruments may also contain stored(e.g., on a semiconductor memory inside the instrument) information thatmay be permanent or may be updatable by the surgical system.Accordingly, the system may provide for either one-way or two-wayinformation communication between the instrument and one or more systemcomponents.

FIG. 1 shows a pictorial view of a minimally invasive teleoperatedsurgical procedure on a patient 110 using a single access port 100 forteleoperated surgical instruments 102, 104, 106. The single access port100 is inserted through a single incision 112. Typically three or foursurgical instruments (instruments 102, 104, and 106 are illustrated),including a camera instrument, are introduced through the single accessport 100. In addition, there will generally be provisions forintroducing an insufflation gas, such as carbon dioxide (CO₂), at ornear the single access port 100. It will be appreciated that single portsurgery uses a substantial amount of equipment located in a small amountof space.

The teleoperated surgical instruments 102, 104, and 106, which mayinclude a camera instrument that may provide images of the surgical siteand other instruments at the surgical site, are each coupled to acorresponding actuator, such as one of actuators 122, 124, 126, and 128.The actuators 122, 124, 126, and 128 are servo actuators that allow asurgeon to manipulate the surgical instruments using a computer-mediatedcontrol station 120. These manipulations may include functions such aschanging the position and orientation of the surgical instrument's endeffector (to include a camera) and operating the end effector (such asclosing jaws to effect grasping, cutting, etc.). Such actuator controlof surgical instruments may be referred to by various terms, such asteleoperated surgery. The actuators 122, 124, 126, and 128 may besupported on a separate structural arm that, once positioned, can befixed relative to the patient 110. In various implementations thesupporting arm may be manually positioned, may be positioned by thesurgeon, or may be automatically positioned by the system as the surgeonmoves one or more of the surgical instruments.

A control system couples a computer-mediated control station 120 to theteleoperated actuators 122, 124, 126, and 128. Here “computer” broadlyencompasses a data processing unit that incorporates a memory and anadditive or logical function, such as an arithmetic logic unit, that isprogrammable to perform arithmetic or logical operations. The controlsystem may coordinate movement of the input devices with the movement oftheir associated surgical instruments so that the images of the surgicalinstruments 102, 104, 106, as displayed to the surgeon, appear at leastsubstantially connected to the input devices in the hands of thesurgeon. Further levels of connection will also often be provided toenhance the surgeon's dexterity and ease of use of the surgicalinstruments 102, 104, and 106.

The computer-mediated control station 120 may provide hand operatedmaster controllers 130 that allow manipulation of the teleoperatedsurgical instruments 102, 104, 106 by transmitting signals, such aselectrical or optical control signals provided by cables 132, to theactuators 122, 124, 126, and 128 that control the actions of the coupledsurgical instruments 102, 104, and 106. Typically one of the surgicalinstruments, surgical instrument 102 for example, will be a camerainstrument that is manipulated to place the remaining surgicalinstruments and the objects being manipulated within a field of view ofthe camera. The camera instrument transmits signals to the controlstation 120 so that an image captured by the camera of the instrumentsand objects within the field of view can be displayed on a visualdisplay 134 that is viewed by the surgeon as the coupled surgicalinstruments 104, 106 are manipulated. The hand-operated controllers 130and the visual display 134 may be arranged to provide an intuitivecontrol of the surgical instruments 104, 106, in which the instrumentsmove in a manner similar to the operator's hand movements with thecontrollers.

FIG. 2 is a pictorial view of an unassembled cannula and instrumentguide assembly that forms an access port 100 which can be insertedthrough the incision 112. The access port 100 is shown before the partsare assembled into the configuration used during a surgical procedure.When assembled, the cannula and instrument guide assembly provides thesingle port access shown in FIG. 1 .

The access port 100 includes a cannula 200 having a lumen 202 that isinserted through the incision 112 to separate and protect the incision.The access port 100 further includes an instrument guide 220 that isinserted into the cannula 200. The instrument guide 220 may be coupledto the cannula 200 in various ways to retain the instrument guide in thecannula during the surgical procedure. The instrument guide 220 guidesone or more instruments through the cannula 200 to facilitate instrumentaccess to the surgical site.

The cannula 200 includes a proximal portion 204 having an insufflationport 206 and a lumen 202 coupled to the proximal portion. Theinsufflation port 206 receives an insufflation gas, such as carbondioxide (CO₂), that is introduced to the surgical site through the lumen202 portion of the cannula 200.

The access port 100 may include a seal assembly 210 that is coupled tothe cannula 200. The seal assembly 210 seals the access port 100 toreduce loss of insufflation gas when the instrument guide 220 is notinserted into the cannula 200.

The instrument guide 220 may be joined to a funnel assembly 230 thatprovides instrument receivers 232 to guide instruments into passages inthe instrument guide at the proximal end of the instrument guide. Thefunnel assembly 230 may include seals that seal the instrument passagesin the instrument guide 220 to reduce loss of insufflation gas when aninstrument is not inserted into an instrument passage. The instrumentguide 220 may include one or more instrument passages. Instrument guidesmay include one, two, three, four, five, six, or more instrumentpassages. The instrument passages may all be the same size and shape orthey may vary in size and/or shape. Each instrument passage may have acircular cross-section or an oval cross-section or other cross-sectionshape that corresponds to the shape of the instrument shaft to besupported by the instrument passage.

The distal portion of the instrument guide 220 is configured to fitclosely within the lumen 202 portion of the cannula 200. Each of the oneor more instrument passages in the instrument guide 220 is configured tosupport a single surgical instrument at a defined position within thecannula 200. The surgical instruments are inserted into the access port100 through the instrument receivers 232 in the funnel assembly 230 sothat they are directed into the instrument passages at a proximal end ofthe instrument guide 220. The surgical instruments are supported by theinstrument passages until they emerge from a distal end of theinstrument guide 220. In some embodiments, the instrument guide 220 maybe formed from an electrically non-conductive material to aid inelectrically isolating the instruments, which may carry an electricalcharge used for electrosurgical applications (e.g., cauterization). Inother embodiments, the instrument guide 220 may be formed from aconductive material, such as metal or conductive plastic, to aid indissipating any electrical charge that might build up on the instrumentspassing through the guide.

In some embodiments, the cannula 200 may be reusable (e.g., aftercleaning and sterilization). Some or all of the instrument guide 220,the funnel assembly 230, and the seal assembly 210 may be provided as asterile, disposable kit, e.g., a gamma sterilized kit, so that a newinstrument guide, a new funnel assembly, and/or a new seal assembly maybe used for each surgical procedure.

FIG. 3 shows a side view of the access port 100 with the cannula 200 cutaway along a diameter to show the instrument guide 220 inserted into thecannula. The instrument guide 220 includes at least one channel 224 onan outer surface 222 of an outer wall of the instrument guide to form apassage for insufflation gas from the insufflation port 206 to thedistal end of the lumen 202 portion of the cannula 200.

The channel 224 is adjacent an interior surface of the lumen 202 to formthe passage for insufflation gas when the instrument guide 220 isinserted into the lumen. The channel 224 extends completely to thedistal end 300 of the instrument guide 220. The channel 224 extendstoward but does not reach the proximal end of the instrument guide 220.The channel 224 extends toward the proximal end sufficiently for theproximal end 302 of the channel to receive insufflation gas that flowsfrom the insufflation port 206 and through the proximal portion 204 ofthe cannula 200.

The seal assembly 210 may include a proximal seal 306 and sealing flaps304. The proximal seal 306 seals the instrument guide 220 beyond theproximal end 302 of the channels 224 to prevent insufflation gas fromescaping past the instrument guide at the proximal end of the cannula200. The sealing flaps 304 are opened when the instrument guide 220 isinserted into the lumen 202. While the sealing flaps 304 appear to blockthe flow of insufflation gas from the insufflation port 206 to theproximal end 302 of the channels, there are openings between the flapsthat allow the flow of insufflation gas throughout the proximal portion204 of the cannula 200. Thus the cannula and instrument guide assemblyof the access port 100 provides a mechanism for introducing insufflationgas into the surgical sites while minimizing the loss of insufflationgas from the assembly.

FIG. 4 is a cross-section of the instrument guide 220 taken alongsection line 4-4. FIGS. 5A and 5B are cross-sections of the instrumentguide 220 taken along section line 5-5. FIG. 5A omits the detail of thechannel end view that is shown in the enlarged view of FIG. 5B.

It is necessary to provide a flow rate of insufflation gas sufficient toinflate the surgical region to a set pressure, perhaps 8 to 14 mm Hg,and replace gas loss due to leakage. Insufflation gas may be supplied ata pressure of about 15 mm Hg (about 2,000 Pa). The flow rate may beabout 20 l/min. It will be appreciated that the velocity of insufflationgas flowing through the one or more channels 224 depends on thecross-sectional area of the channel. The flow will have a highervelocity when the cross-sectional area is small and a lower velocitywhen the cross-sectional area is large. But it is desirable to have asmall cross-sectional area for the one or more channels 224 to minimizethe diameter of the instrument guide 220 and the cannula's lumen 202.The cross-sectional area for the one or more channels 224 is constrainedby the need to maintain a certain wall thickness for the structuralintegrity and manufacturability of the instrument guide 220.

It is also desirable to avoid high velocity flow of insufflation gasthat can disturb or even damage tissues adjacent the distal end of thecannula 200 where the insufflation gas is discharged into the surgicalsite. To provide a small diameter instrument guide 220 while minimizingthe discharge velocity of insufflation gas, the one or more channels 224having a first cross-sectional area at a proximal end of the channel anda second cross-sectional area at a distal end of the channel that islarger than the first cross-sectional area.

The one or more channels 224 have the first cross-sectional area for themajority of the length of the channel. A transitional section 308 beginsclose to the distal end of the channel 224 to provide a transition tothe second cross-sectional area. The transition is made just long enoughto avoid introducing turbulence in the flow of the insufflation gas. Insome embodiments, the transition from the first cross-sectional area tothe second cross-sectional area is about 1 inch (about 25 mm) long. Bylimiting the larger cross-sectional areas to the distal end 300 of theinstrument guide 220, the adverse consequences of the largercross-sectional areas are minimized. This allows the instrument guide220 to have a smaller diameter than would be possible if the channel 224had the second cross-sectional area for its entire length. In someembodiments, the second cross-sectional area is at least twice the firstcross-sectional area, reducing the discharge velocity of theinsufflation gas to half or less than the velocity at the proximal endof the channel. For example, in one embodiment the first cross-sectionalarea is about 0.0023 in² (1.5 mm²) and the second cross-sectional areais about 0.0050 in² (3.0 mm²).

The one or more channels 224 are located relative to the interiorpassageways to provide a first wall thickness for the instrument guidewhere the channel has the first cross-sectional area and a second wallthickness for the instrument guide where the at least one channel hasthe second cross-sectional area, the second wall thickness being lessthan the first wall thickness.

FIG. 6 shows a schematic side view of the instrument guide 220 insertedinto the cannula 200 to illustrate the flow of insufflation gas from theinsufflation port 206 to the surgical site 602. The double dashed arrowssuggest the flow of insufflation gas 600. The cannula 200 is insertedthrough an incision 112 which seals against the outside of the cannula.The proximal portion 204 of the cannula 200 forms a plenum that suppliesinsufflation gas. The proximal portion 204 is sealed at the proximal endby the proximal seal 306 sealing against the instrument guide 220.

Insufflation gas enters the one or more channels 224 on the outersurface 222 of the instrument guide 220 from the plenum formed by theproximal portion 204 of the cannula 200 and flows toward the distal end300 of the instrument guide. The one or more channels 224 include atransition section 308 that has an increasing cross-sectional area atthe distal end 300 of the channels. As suggested by the reduced lengthof the double dashed arrow in the transition section 308, the increasingcross-sectional area of the transition section reduces the velocity ofthe insufflation gas before it is discharged into the surgical site 602.

The instrument guide may be manufactured by injection molding of aplastic resin. As is well known in the plastic molding industry, thereare numerous design guidelines that must be considered to design a partthat can be successfully manufactured by an injection molding process.Many of these guidelines are based on the need to cause the plasticresin to fill the mold when the heated plastic resin is forced into themold under pressure.

One guideline for injection molding limits the length of thin sectionsso that the plastic resin does not harden excessively before reachingthe end of the thin section. A desirable plastic for manufacturing aninstrument guide is a polycarbonate resin, such as Calibre™ Megarad™2081-15 polycarbonate resin from Trinseo S.A., because of itsdimensional stability and durability. The length of a thin wallmanufactured from injection molded polycarbonate resin is limited toless than one hundred times the thickness of the wall. An instrumentguide may be about 5 inches (about 125 mm) in length and thus requirethe use of wall thicknesses of 0.050 inches (1.25 mm) or greater. Thisthickness is difficult to provide in an instrument guide having anoutside diameter of less than 1 inch (25.4 mm) and having passages forfour instruments, one of which is a camera, a typical requirement for aninstrument guide.

FIGS. 7 through 10 are cross-sections of an exemplary instrument guidetaken along the same section line 4-4 as the cross-section shown in FIG.4 , illustrating a design process for designing an instrument guide tobe manufactured by an injection molding process. These cross-sectionscould also be applied to the embodiments already described.

FIG. 7 shows a cross-section of the outside surfaces of a camerainstrument 702 and three additional surgical instruments 704, 706, 708and the outside surface 722 of the instrument guide. As illustrated, thecamera instrument has an oval cross section, and the three additionalinstruments have round cross sections. The camera instrument 702 and thethree additional surgical instruments 704, 706, 708 are placed withinthe outside surface 722 of the instrument guide such that the minimumspace between adjacent instruments is substantially the same, assuggested by the model radial walls 712, 714, 716, 718 drawn with dashedlines. Likewise, the minimum space between the outside surface 722 ofthe instrument guide and the adjacent instruments 702, 704, 706, 708 issubstantially the same as the radial wall separation as suggested by themodel outer wall between outside surface 722 and circular dashed line724.

To ensure the desired tight (ideally, tightest possible) packing withinthe cannula, the instruments may be placed using analytic techniques orby iterative graphical methods, which may be more effective wheninstruments of differing geometries, such as the camera instrument 702,are being placed. The camera instrument 702 may house a stereoscopiccamera, such as the one disclosed in U.S. Pat. No. 8,556,807 B2 (filedMay 15, 2010), that requires the outside surface of the camerainstrument to have a generally oval shape. The outside surface of thecamera instrument may be in the form of a four circular curveapproximation to an ellipse. The use of circular curve segments to formthe outside surface of the camera instrument may simplify constructionof the camera instrument and/or the instrument guide.

In one exemplary embodiment of an instrument guide, the outside surfaceof the instrument guide has a diameter of about 1 inch (about 2.54centimeters) and it is about 5 inches (about 12.7 centimeters) inlength. The larger curved surfaces of the exemplary camera instrumenthave a radius of about 0.4 inches. The remaining surgical instrumentsare about 0.3 inches in diameter. The minimum space between adjacentinstruments and between the outside surface of the instrument guide andthe adjacent instruments is about 0.03 of an inch. It will beappreciated that the exemplary instrument guide cannot be injectedmolded from a polycarbonate resin with walls this thin because of thelength of the guide.

FIG. 8 shows a cross-section of an instrument guide in which the radialwalls 812, 814, 816, 818 and the outer wall 824 have been increased inthickness except for the areas 802, 804, 806, 808 where the placement ofthe instruments requires the walls to be thinner. These thinner areasform guideways 802, 804, 806, 808 for the instruments—guideways 802 forinstrument 702, guideways 804 for instrument 704, guideways 806 forinstrument 706, and guideways 808 for instrument 708. The radius of eachof these guideways corresponds to the radius of the instrument itreceives to allow a sliding fit, which may help stabilize theinstruments laterally within the instrument guide and may help theinstruments move more easily in an axial direction as they are insertedinto and withdrawn from the instrument guide. It will be appreciatedthat the axial motion of the instruments in the guide may provide oneaxis of motion for an instrument as it is used in a surgical procedure.In the exemplary embodiment of an instrument guide, the walls 812, 814,816, 818, 824 may be increased to a thickness of about 0.05 inches,which is sufficient for injection molding requirements, despite therelatively thinner areas at the guideways. Stated another way, thegeneral thicknesses of each of the radial walls and the outer wall aresubstantially the same and are sufficient for injection molding for thelengths of the walls, but the thicknesses of the radial and outer wallsin portions of the walls where a guideway is formed is less than thegeneral thickness, and these lesser thicknesses has been foundacceptable for injection molding.

It can be seen in FIG. 8 that one side of a radial wall partiallydefines a first passageway, and the reverse side of the radial wallpartially defines a second passageway. Thus as illustrated a guidewayfor the first passageway is formed in one surface of a radial wall, anda second guideway for the second passageway is formed in the reversesurface of the radial wall. In the illustrated embodiment the guidewaysare generally opposite one another in the obverse and reverse surfacesacross the wall, although in other instrument placement geometries theguideways formed in a single wall may be offset from one another acrossthe wall.

FIG. 9 shows a cross section of the instrument guide in which the “V”where the radial walls 812, 814, 816, 818 intersect has been joined by aradius 904, 906, 908. In the three passageways for the surgicalinstruments, the instruments 704, 706, 708 do not occupy the “V” region.Therefore, it is possible to join the walls with a large radius.Preferably the joining radius is smaller than the outside radius of thesurgical instruments so there is a substantial clearance between thejoining radius and the instrument. The passage way for the camerainstrument 702 is such that the instrument guideway 802 may be used asthe joining radius rather than removing material at the intersection ofthe walls to provide a clearance guideway. In the exemplary embodimentof an instrument guide, the joining radii may be 0.05 to 0.10 inches.

Joining the radial walls 812, 814, 816, 818 with large radii creates asolid central core 900 that is much thicker than the radial walls andthe tube's outer wall 824. While conventional design practice forinjection molded parts avoids joining thick sections to thin sectionsbecause of warpage and shrinkage issues, it has been found that a thicksolid central core can be used in the instrument guide because the guideis symmetrically supported by the radial walls, and the solid centralcore does not provide any critical surfaces in the guide. Providing athick solid central core provides a good flow path for the plastic resinduring injection molding and has been found to overcome the issuescommonly associated with creating long thin walls by injection moldingbecause the resin flows from the core outward through the radial wallsand into the outer wall.

The central core has a minimum “diameter” that is substantially largerthan the wall thickness, where “diameter” means the diameter of thelargest circular cylinder that could be contained within the core. Inthe exemplary embodiment of an instrument guide, the central core may belarger than a cylinder with a diameter of 0.15 inches as suggested bythe dashed circle shown over the core. Thus the central core may beabout three times the thickness of the thickened portions of the wallsand more than four times the thickness of the thinnest portions of thewalls at the guideways. The core has a minimum diameter that issubstantially larger than the wall thickness

FIG. 10 shows a cross-section of an instrument guide in which channels1000 for insufflation gas have been added to the outside surface 722 ofthe instrument guide, as described previously. The channels are formedin the outer wall and centered over the radial walls 812, 814, 816, 818.This position allows the channels to be formed without interfering withthe placement of the instruments. The thickness of the outer circularwall can be kept substantially constant across the insufflation gaschannels. The distal portion of the channels may be enlarged to providea larger cross-section area as described previously. In someembodiments, a small radius is used where the radial walls meet theouter wall.

FIG. 11 shows a side view of an exemplary instrument guide 1100. FIG. 12shows an end view of the exemplary instrument guide 1100. FIG. 13 showsa cross-sectional view of the exemplary instrument guide 1100 takenalong line 13-13 in FIG. 12 . FIG. 14 shows a schematic representationof a mold that can be used to produce an instrument guide by injectionmolding.

To facilitate release of an injection molded part from the mold,surfaces are generally provided with draft, a small angle to the surfaceso that the part separates from the mold as the part moves out of themold. For example, the passageways 1102, 1104 have a smaller opening1108 at the distal end of the instrument guide and a larger opening 1106at the proximal end. Conversely, the tube walls 1110 and the core 1112have a thicker cross section at the distal end of the instrument guideand a thinner cross section at the proximal end. Thus the passageways1102, 1104 will separate from the mold as the instrument guide moves ina distal direction relative to the mold. The amount of draft shown inFIG. 13 has been greatly exaggerated so that the draft can be seen. Theillustrative cross section clearly shows the much greater thickness ofthe core 1112 relative to the tube walls 1110.

Design guidelines for injection molding recommend at least one-halfdegree of draft and suggest one degree or more of draft as a preferredpractice. One-half degree of draft will create almost 0.1 inches (almost2.5 millimeters) more clearance between an instrument and the guidewaypassage at the proximal end than at the distal end of a 5 inch (12.7centimeter) long passageway. But, 0.1 inches (2.5 millimeters) ofadditional clearance at the proximal end of the passageway would allowexcessive movement at the distal end of the instrument. In practice,0.13 degrees of draft creates less than 0.03 inches (0.76 millimeters)more clearance at the proximal end and controls the position of thedistal end of the instrument acceptably. Special design considerationsdescribed below are used to allow separation of the part from the moldwith this small amount of draft.

The instrument guide includes a flange 1120 that extends outwardly fromthe proximal end 1122 of the tube. Referring to FIG. 14 , the flange maybe formed in a cavity 1402 of a first mold segment 1400. The passagewaysmay be formed by a second mold segment 1410 that includes cylindricalsegments 1412 that form the passageway openings and the guideways. Thecylindrical segments 1412 pass through openings 1404 in the first moldsegment 1400. The cylindrical segments 1412 are ejected from the moldedinstrument guide by moving the second mold segment 1410 away from thefirst mold segment 1400 in the direction suggested by the arrow 1414 onthe second mold segment. The support provided by the flange 1120 in the1402 of the first mold segment 1400 allows the cylindrical segments 1412to be withdrawn from the instrument guide and pass through the openings1404 in the first mold segment 1400 despite having much less than thenormal amount of draft for ejecting a part from a mold.

The outside surface of the tube has the same outside diameter from thedistal end 1124 to the proximal end 1122 so that the instrument guide isstably positioned within the cannula 200 (FIG. 3 ). This uniform outsidediameter requires the use of side action mold segments 1420, 1430 thateach include a cavity 1422 that forms one-half of the outside surface ofthe tube and the insufflation passages. The side action mold segments1420, 1430 move away from the molded instrument guide in oppositedirections from one another as suggested by the arrows 1424, 1434 on themold segments.

It has been found that two gate sites 1126 can be placed atdiametrically opposed locations on the periphery of the flange 1120 toreliably fill the instrument guide mold cavity. These locations are notdimensionally critical, and the gate site vestiges can be readilytrimmed.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat this invention is not limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those of ordinary skill in the art. For example, while the useof the channels of the instrument guide have been described for thedelivery of insufflation gas to the surgical site, the same or similarchannels can be used to evacuate gases and/or smoke from the surgicalsite. The description is thus to be regarded as illustrative instead oflimiting.

The invention claimed is:
 1. A medical device comprising: an instrumentguide comprising a tube, a solid core, and a plurality of radial walls;the tube having a proximal end, a distal end, and an outer wall; thesolid core extending from the proximal end to the distal end of thetube; and the plurality of radial walls extending from the proximal endto the distal end of the tube and from the solid core to the outer wallof the tube, each adjacent pair of the plurality of radial walls formingone of a plurality of passageways bounded by the solid core and thetube; wherein a thickness of the outer wall of the tube and a thicknessof each individual radial wall of the plurality of radial walls aresubstantially the same first thickness, and the solid core has a minimumdiameter that is substantially larger than the first thickness, whereina first instrument guideway is formed in a surface of a first radialwall of the plurality of radial walls, and wherein a second thickness ofthe first radial wall at the first instrument guideway is less than thefirst thickness.
 2. The medical device of claim 1, wherein a firstinstrument guideway is formed in the outer wall of the tube; and whereina second thickness of the outer wall of the tube at the first instrumentguideway is less than the first thickness.
 3. The medical device ofclaim 1, wherein a first instrument guideway is formed in the outer wallof the tube that defines a first passageway of the plurality ofpassageways, and a second thickness of the outer wall of the tube at thefirst instrument guideway is less than the first thickness; and whereina second instrument guideway is formed in a first radial wall of theplurality of radial walls that defines the first passageway, and a thirdthickness of the first radial wall at the second instrument guideway isless than the first thickness.
 4. The medical device of claim 1, whereineach of the plurality of passageways includes three guideways, oneguideway of the three guideways formed by a thin portion of the outerwall of the tube, and the remaining two guideways of the three guidewaysformed by a thin portion of each of the adjacent pair of the pluralityof radial walls forming the plurality of passageways.
 5. The medicaldevice of claim 1, wherein the first radial wall of the plurality ofradial walls comprises a first surface and a second surface reverse ofthe first surface; wherein the first instrument guideway is formed inthe first surface and a second instrument guideway is formed in thesecond surface; and wherein the third thickness of the first radial wallbetween the first instrument guideway and the second instrument guidewayis less than the first thickness.
 6. The medical device of claim 1,wherein an outside diameter of the tube is constant from the distal endto the proximal end.
 7. The medical device of claim 6, wherein the firstthickness is less at the proximal end than at the distal end of thetube, causing each of the plurality of passageways to be larger at theproximal end of the tube than at the distal end of the tube.
 8. Themedical device of claim 7, formed by injection molding.
 9. The medicaldevice of claim 1, wherein the first instrument guideway is defined by aconstant radius curve.
 10. The medical device of claim 1, wherein aninsufflation gas channel is defined in an outer surface of the outerwall of the tube; and wherein the insufflation gas channel flaresoutward at the distal end of the tube.
 11. The medical device of claim10, wherein the insufflation gas channel is further defined in the outersurface of the outer wall of the tube opposite a location where one ofthe plurality of radial walls joins the outer wall.
 12. The medicaldevice of claim 10, wherein the outer wall of the tube maintains thefirst thickness at the insufflation gas channel.
 13. The medical deviceof claim 1, wherein the tube includes a plurality of insufflation gaschannels formed on an outside surface of the tube, each of the pluralityof insufflation gas channels extending from the distal end of the tubetoward the proximal end and centered over a corresponding one of theplurality of radial walls.
 14. The medical device of claim 13, whereineach of the plurality of passageways is shaped such that the thicknessof the outer wall of the tube remains substantially the same at theplurality of insufflation gas channels.
 15. The medical device of claim13, wherein each of the plurality of insufflation gas channels has alarger cross-sectional area at the distal end of the tube than at theproximal end of the tube.
 16. The medical device of claim 13, whereineach of the plurality of insufflation gas channels extends toward butdoes not reach the proximal end of the tube of the instrument guide. 17.The medical device of claim 1, further comprising a flange extendingoutwardly from the proximal end of the tube.
 18. The medical device ofclaim 1, further comprising: a cannula including a proximal portionhaving an insufflation port, the cannula having a lumen extending fromthe proximal portion of the cannula; and the instrument guide removablyinserted into the proximal portion of the cannula and extending throughthe cannula to a distal end of the lumen.
 19. The medical device ofclaim 18, wherein the tube includes a plurality of insufflation gaschannels adjacent an interior surface of the lumen to form a passage forinsufflation gas.
 20. The medical device of claim 1, further comprising:a funnel assembly joined to the proximal end of the tube of theinstrument guide, the funnel assembly comprising a plurality of funnels,each funnel of the plurality of funnels corresponding to a correspondingone of the plurality of passageways.